1. Field of the Invention
This invention relates generally to photographic film processing apparatus. More particularly, the invention relates to a film leader card for use in a film processor to transport a filmstrip attached to the card through one or more film processing baths.
2. Description of the Prior Art
The processing of photographic film involves a sequence of solution-treating steps such as developing, bleaching, fixing, and rinsing. These steps lend themselves to mechanization by conveying long strips of film sequentially through a series of adjacent stations or tanks, each one containing a processing solution appropriate to the process step at that station.
One type of known film processor employs a film leader card which is advanced to pull one or more filmstrips attached to the card along respective processing racks in successive processing tanks or stations in the processor. The leader card is advanced through the film processor by respective endless timing belts moving around the successive racks, and is guided by a crossover member from one rack to the next one. The leader card has a series of holes for engagement with respective projections on each timing belt. Typically, the holes in the leader card are evenly spaced and identical in size to match the pitch of the projections on the timing belts.
U.S. Pat. No. 4,613,221, issued Sept. 23, 1986 to Takase et al, discloses a film processor of the type having a succession of endless timing belts with evenly spaced projections for engaging a leader card to advance a filmstrip attached to the card through the processor. The Takase patent shows a leader card having a plurality of evenly spaced holes for engagement with the respective projections on each timing belt. The holes and the projections have the same pitch. A potential problem associated with the leader card, due to the match in the pitch of the holes and the projections, involves the possibility of interference between the card and the projections during transfer of the card from one timing belt to another timing belt. Specifically, one way in which this problem manifests itself is that a leading area of the leader card, when trying to first engage the next timing belt, may "stub" on a projection on that belt and thus not engage properly with the belt. See FIG. 2 in the accompanying drawings. The other side of the problem is that a trailing area of the leader card, when trying to disengage from the last timing belt, may "hang up" on a projection on that belt and thus not be able to disengage from the belt. See FIG. 3 in the accompanying drawings. Further detail as to these problems is provided below.